Fastening systems such as shackles are commonly used in a variety of industries to secure two or more objects to each other. For example, construction workers may use a shackle to secure a heavy load to a crane. Tow truck drivers may utilize a shackle to secure a vehicle to a tow truck. Or sailors may use a shackle to fasten a ship to a dock. Typically, shackles have a U or C-shaped housing having two legs, each of which has an opening for the passage of a clevis or locking pin. Unsurprisingly, it is desirable for manufacturers of shackles to ensure that the locking pin does not completely separate from the housing; separated locking pins are prone to being misplaced, and a missing locking pin prevents the shackle from being used as desired. Complex mechanisms have been developed to ensure retention of the locking pin with the housing. For example, U.S. Pat. No. 6,023,927 to Epstein discloses a shackle having a U-shaped member, a locking lever having an outwardly projecting finger, and a clevis pin having two perpendicular grooves therein that allow for the passage of a clevis pin and prevent the clevis pin from separating from the U-shaped member. Drawbacks remain in prior art shackles, however (e.g., complications in manufacturing, difficulties in use, attention that must be paid not to clog relatively small openings in locking pins, etc.), and new quick release fastening systems that may overcome some of these and/or other deficiencies are desirable.